This invention relates in general to vehicle transmissions, and in particular to sensing vibration or other operating conditions of various parts of vehicle transmissions.
In most vehicles, a transmission is provided in the drive train between the engine and the driven wheels. As is well known, the transmission includes a plurality of gears which are selectively engaged to provide a plurality of speed reduction gear ratios between the input and the output of the transmission. A plurality of control members, such as clutch collars, contained within the transmission are moved by a driver of the vehicle throughout a plurality of gear ratio positions for selecting the desired speed reduction. As a result, acceleration and deceleration of the vehicle can be achieved in a smooth and efficient manner.
Typical transmission structure includes an input shaft, a countershaft, and a mainshaft. Gears positioned between the input shaft and the countershaft drive the countershaft at a rotation speed proportional to the engine speed. Countershaft gears of different sizes are rigidly mounted on the countershaft for rotation, and these also rotate at speeds proportional to the engine speed. For example, the gears mounted on the countershaft could be forward gears one though five, plus reverse. The countershaft and the countershaft gears will always rotate at the same speed relative to each other since they are all mechanically linked together.
The countershaft gears drive another set of gears, the mainshaft gears, which are complementary to the countershaft gears. The mainshaft gears are mounted co-axially with the mainshaft, but not directly linked to the mainshaft. Since each of the mainshaft gears is rotated by meshing with the teeth of a different sized countershaft gear, each mainshaft gear is rotating at a speed different from every other mainshaft gear, but at a speed proportional to the engine speed. It is the clutch collars which cause the linkage between the rotating mainshaft gears and the mainshaft. Axial movement of one of the clutch collars causes the splines of the clutch collar to link the associated mainshaft gear with the mainshaft, thereby causing a mechanical link all the way from the input shaft to the mainshaft. The mainshaft then rotates at a speed which is proportional to engine speed.
The transmission assembly so far described can be referred to as the main section, and there is frequently provided, downstream or rearwardly of the main section, an auxiliary transmission section which includes two or more speed reduction gear ratios, thereby compounding the gear ratio options of the entire transmission assembly. The eventual output from the transmission assembly is through the output shaft, which is typically connected via a universal joint to the drive shaft.
The rotating parts in the transmission assembly, including the input shaft, countershaft, mainshaft and output shaft are all mounted for rotation on bearings. Lubrication is required for the bearings as well as for the gears themselves with their intermeshing teeth. Typically, the transmission is contained within a transmission case or housing, which facilitates containment of the lubricants. Although the countershaft and mainshaft gears are always rotating, the load or torque on the gears and on the bearings will vary with the gear selected. For example, the load on the rear countershaft bearing will be higher for a lower gear than for a higher gear.
One of the problems with vehicle transmissions is that various parts are subject to wear and eventual failure. A prime example of transmission parts that are subject to failure is any one of the numerous sets of bearings associated with the many rotating parts of a transmission. Often there are subtle changes in the vibration patterns of a vehicle transmission part as it wears out or begins to fail. Therefore it would be helpful to be able to detect changes in vibration patterns.
The changes in vibration patterns are not always perceptible to the vehicle operator prior to the actual failure of the part. It would be advantageous if the vehicle driver were alerted to these subtle changes in vibration and the associated likelihood of failure of a part of the vehicle transmission. Also, even when the vehicle driver perceives a change in the vibration pattern, it is not always possible to determine the exact source of the vibration, or even the general area or zone of the transmission causing the vibration. Therefore it would be advantageous to have a diagnostic tool which would enable the source of vibration to be pinpointed or at least localized to a specific zone or area of the transmission. Any solution to the problem of detecting or diagnosing vibration should be relatively inexpensive, simple to operate and generally maintenance free. Ideally, any transmission vibration monitoring system would make use of existing diagnostic or control equipment and data sources already on board the vehicle.